1. Field of the Invention
The present invention relates to a gain control circuit and method, especially to a gain control circuit and method capable of easing leakage current influence.
2. Description of Related Art
Generally an adjustable gain circuit or a gain circuit for mixed-signal input has a plurality of gain paths as operation options. Each of the gain paths has a switch, and the on/off states of these gain paths will determine one among the gain paths as the working path; in other words, through the control over the switches, one of the gain paths will be conducting while the others will be non-conducting, so that the conducting path will be responsible for amplifying an input signal. In a normal case, the switches are realized by MOS transistors; however, MOS transistors inevitably suffer from leakage current especially when the amplitude of the input signal is getting high, which means that some of the MOS transistors supposed to be non-conducting will leak current due to the input signal of high amplitude. In the meantime, the leakage current will interfere with the conducting path and lead to the increase of total harmonic distortion (THD).